Calciner technology for optimized use of alternative fuels in cement kilns

In modern cement kiln systems there are two burning zones; one in the precalciner, where most of the carbonate in the raw meal is decomposed into calcium oxide and carbon dioxide, and another one in the rotary kiln outlet. The precalciner, which operates at the lowest temperature (typically 850-1200 °C), offers the greatest potential of using alternative fuels.


Different precalciner designs are available from different suppliers; some of them are more suitable for burning large amounts of alternative fuels.

Residence time, temperature distributions, oxygen availability, turbulence levels and velocity distributions are key parameters in determining the characteristics of a good precalciner design.

Increased use of lumpy alternative fuels may have a negative impact on the internal cycles of sulphur, alkalis and chlorine in the kiln system. By good precalciner designs, such negative impacts can be avoided or considerably reduced.

Currently there is an ongoing PhD project, "Optimised and increased use of refuse derived fuel in cement kilns" (PhD student: Amila Chandra Kahawalage) in cooperation with the Norwegian cement manufacturer Norcem AS (part of Heidelberg Cement Group). Factors impacting (limiting) the use of partly CO2 neutral fuels are investigated, and different approaches are applied:

  • Testing of different fuels and fuel mixtures in full-scale trials
  • Energy balances of the calciner system by use of models implemented in Matlab
  • Investigation of flow and combustion behaviour of different types of fuel in the main burner by applying computional fluid dynamics (CFD) simulations (using Fluent and Barracuda)

References

Kahawalage, A.C., Melaaen, M.C. and Tokheim, L.A.: "Numerical Modelling of the Calcination Process in a Cement Kiln System", Linköping Electronic Conference Proceedings (Proceedings of the 58th SIMS September 25th - 27th, Reykjavik, Iceland), pp. 83-89, 2017

Kahawalage, A.C., Melaaen, M.C. and Tokheim, L.A.: "Substitution of coal by refuse derived fuels (RDF) in the precalciner of a cement kiln system", 7th International conference on Energy and Sustainability, Seville, Spain, 20-22 September, 2017

Tokheim, L.A. and Brevik, P.: "Carbon dioxide emission reduction by increased utilization of waste-derived fuels in the cement industry", Proceedings, International Conference on Sustainability in the Cement and Concrete Industry, Lillehammer, Norway, 16-19 September 2007

Tokheim, L.A.: "Burning chamber installation for increased use of alternative fuels at Norcem Brevik", Proceedings, 7th International KHD Humboldt Wedag Symposium, Cologne, Germany, 17‑19 May 2006

Tokheim, L.A.: "Kiln system modification for increased utilization of alternative fuels at Norcem Brevik", Cement International, No. 4, 2006

Tokheim, L.A.: " An alternative solution", World Cement China, 23, No. 3, 19-24, 2006

Tokheim, L.A.: "An alternative solution", World Cement, 22, No. 11, 57-63, 2005

Tokheim, L.A., Gautestad, T., Axelsen, E.P and Bjerketvedt, D.: "Energy recovery of wastes: Experience with solid alternative fuels combustion in a precalciner cement kiln", Conference proceedings, International Symposium on Incineration and Flue Gas Treatment Technologies, 3, Brussels, 2-4 July 2001